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Cannot remove Encrypted Volume after Mountion Lion Rebuild

If you’ve rebuilt your Operating System on Mountain Lion, and previously you encrypted your TimeMachine backups, you may find you can’t repartition the drive. Here’s how to get around it.


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I recently rebuilt my Mountain Lion build on my main Macbook Pro - mainly because I’d broken it while messing around with some beta software. A risk you take I guess. Anyways, I ran in to an oddity with a couple of encrypted drives - first one had FileVault enabled, and the TimeMachine drive had previously been encrypted. Essentially, Disk Utility wouldn’t let me repartition them - the options were greyed out:

CannotPartitionBigBoy

The drive would let you erase, but you couldn’t repartition. If you tried to re-use it for TimeMachine it would want to go through a length decrypt process first..Not pleasant. Essentially the problem comes down to the encrypted volumes containing Core Storage volume groups - you cannot partition the drive while these are present.

Fortunately, there’s an easy way around this in Terminal. Fire up terminal and type in this command:

diskutil cs list

This will present you with a list of the core storage volumes, similar to this:

CoreStorage

Select and copy the UUID from the logical volume group at the top - that’s what we want to delete:

CoreStorageUUID

So to delete that group, use the following command:

diskutil cs delete UUID Copied from earlier

..so for mine, the command would be:

diskutil cs delete ABA216B2-08C5-4E60-99BC-D61F98422176

Running this command deletes the volumes:

DeleteCoreStorageviaUUID

You can now go on and partition the drive how you require.



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